1. Field of the Invention
The invention relates to a method of manufacturing a semiconductor device such as a semiconductor storage device, and in particular to a method of forming multilayer interconnection comprising metal alloy interconnection that has an excellent EM lifetime (EM resistance).
2. Description of Related Art
In general, interconnection layers made of metal alloys are widely used in semiconductor devices. In particular, aluminum alloys (Al alloys) are widely used as interconnection materials, due to having low electrical resistance and being excellent in terms of workability.
It is known that, in a semiconductor device manufacturing process, if nitrogen gas is present when depositing an Al alloy interconnection layer, then the Al crystal grain size will be reduced, and voids will become prone to occurring in the Al alloy interconnection layer. As a result, the film quality drops. Consequently, when depositing an Al alloy interconnection layer by sputtering, the deposition has been carried out with it being a condition that the atmosphere in the deposition chamber substantially does not contain nitrogen.
It is known that in the case that an Al alloy interconnection layer is nitrided, the electrical resistance increases, and hence defects in electrical continuity are brought about.
In recent, there have been advances in making the interconnection in semiconductor devices yet finer and thinner. As a result, the cross-sectional area of the interconnection becomes smaller, and hence the current density increases. With interconnection formed using a conventional Al alloy interconnection formation method, as the current density increases, the electromigration (EM) lifetime becomes shorter. As a result, a problem of the reliability of the manufactured semiconductor device dropping arises.
Consequently, a method of forming Al alloy interconnection layers, in particular Alxe2x80x94Cu interconnection layers, which have been used in many semiconductor devices in recent years, having an excellent EM lifetime is desired.
The inventors involved in the present application thus carried out assiduous studies into what effects nitrogen getting in has on the EM lifetime of the formed interconnection when forming an Al alloy interconnection layer, and as a result arrived at the conclusion that if an Al alloy interconnection layer is formed in the presence of a small amount of nitrogen gas in the atmosphere in the sputtering deposition chamber during deposition, then a semiconductor device having interconnection that has an excellent EM lifetime can be obtained, thus accomplishing the present invention.
According to a method of manufacturing a semiconductor device of the invention, deposition of a metal interconnection layer is carried out with a nitrogen concentration in an atmosphere in a sputtering deposition chamber made to be higher than 12 ppm but lower than 1000 ppm.
If this is done, then the EM lifetime can be improved compared with the case that an Alxe2x80x94Cu interconnection layer is formed under a condition that the atmosphere in the deposition chamber substantially does not contain nitrogen.
The method of manufacturing a semiconductor device of the present invention can be implemented merely by making a small amount of nitrogen be present in the atmosphere in the deposition chamber when depositing a metal interconnection layer by sputtering in a conventionally used interconnection formation method. The EM lifetime of the formed interconnection layer can thus be improved easily, without requiring an increase in the number of manufacturing steps or a new apparatus.